PS 101

1. PS 101 Kim Cohn Email address Kcohn@academic.csubak.edu Chem Review - 2

2. Grades Grades for the first three exams are posted outside my office. Sci 252 Chem Review - 2

3. 1) What elements tend to form ionic compounds? A) those found in the upper right hand side of the periodic table B) elements found on opposite sides of the periodic table C) metallic elements D) Any two elements of the same phase can form an ionic compound. Chem Review - 2

4. 2) What type of chemical bond would you expect between two chlorine atoms (Cl, atomic number 17)? A) metallic B) ionic C) nonpolar covalent D) polar covalent Chem Review - 2

5. 3) The atoms of materials that conduct electricity best tend to be held together by A) polar covalent bonds. B) metallic bonds. C) ionic bonds. D) covalent bonds. Chem Review - 2

6. 5) Salts are made of elements found on opposite ends of the periodic table because elements on A) Not true! Salts are generally made of elements found on the same side of the periodic table. B) opposite ends of the periodic table have similar arrangements of electrons. C) the far left tend to form positive ions while those on the right tend to form negative ions. D) the far left tend to form negative ions while those on the right tend to form positive ions. Chem Review - 2

7. 6) Atoms of a covalent bond are held together by the A) gravitational attraction between the two atoms. B) electrical attraction two nuclei have for shared electrons. C) nuclear attraction between the two nuclei. D) electrical attraction between shared electrons. Chem Review - 2

8. 7) The atoms of a polar covalent bond A) must be of different elements. B) are always of the same element. C) must include a metal and a nonmetal. D) Two of the above are correct. Chem Review - 2

9. 8) Why do nonpolar substances tend to boil at relatively low temperatures? A) Nonpolar substances are not good conductors of heat. B) Not much heat is required to separate nonpolar molecules from one another. C) If they did not boil at low temperatures, they wouldn't be gases at room temperature. D) generally speaking non-polar compounds are not as massive as polar compounds. Chem Review - 2

10. 9) Water molecules are attracted to sodium chloride because A) the dipoles of water are attracted to the ionic charges. B) of the hydrogen bonding between water molecules. C) water molecules are small enough to fit within the crystal lattice. D) of the great attraction between sodium and chlorine ions. Chem Review - 2

11. 10) How does a solid phase differ from a liquid phase on the molecular level? A) There are molecular interactions in the solid phase but not in the liquid phase. B) The molecules of a solid are fixed, while the molecules of a liquid are mobile. C) The molecules of a solid are always more compact. D) Solids have crystalline structure while liquids are amorphous. Chem Review - 2

12. 11) Are there hydrogen bonds between water molecules in the liquid phase? A) No, and if there were the water would just be ice (a solid). B) No, otherwise the water molecules would not be able to tumble over one another. C) Yes, but they rarely occur. D) Yes, and they are continually breaking and reforming. Chem Review - 2

13. 12) When a solution is concentrated, A) large amounts of solute are dissolved in solvent. B) so much solute has been added that the solution is about to solidify. C) large amounts of solvent are dissolved in solute. D) most all of the water has been taken out. Chem Review - 2

14. 13) Fish breathe oxygen, O2, dissolved in the water. Since water is a polar substance and oxygen is a nonpolar substance, how can there be any oxygen, O2, in the water? A) Water induces a dipole in O2 and the two attract one another by dipole-induced dipole molecular interactions. B) Normally there isn't O2 in the water. The gills of fish, however, are equipped to break water down into O2, which stays in the water for short periods of time by dipole-induced dipole molecular interactions. C) The plants in water produce O2 during photosynthesis. The O2 released by the plants floats to the surface in small pockets that fish capture. D) O2 gets caught in the spaces between the water molecules, and only the weight of the water above keeps the oxygen from floating away. Chem Review - 2

15. 4) If gallium ions have a 3+ charge and a sulfur ions have a 2- charge, the compound gallium sulfide is A) Ga3S2. B) Ga2S3. C) Ga6S6. D) Ga4S3. Chem Review - 2

16. 14) "Soft water" is water that A) is difficult to obtain. B) contains a relatively large amount of calcium and magnesium ions. C) contains many dissolved gases. D) none of the above. Chem Review - 2

17. 15) Which set of coefficients balance the following chemical equation? __ PH3 + __ O2 __ P4O10 + __ H2O A) 4, 6, 1, 3 B) 2, 8, 1, 3 C) 4, 8, 1, 6 D) 2, 4, 1, 6 Chem Review - 2

18. 16) The difference between an exothermic and endothermic reaction is that an exothermic reaction A) requires a continual supply of energy but an endothermic reaction does not. B) absorbs energy but an endothermic reaction releases energy. C) has energy as a product and an endothermic reaction has energy as a reactant. D) occurs at a high temperature while endothermic reactions occur at a low temperature. Chem Review - 2

19. 17) Which is true of a reaction that has reached chemical equilibrium? A) The forward reaction rate is equal to the reverse reaction rate. B) The forward and reverse reactions have essentially stopped. C) Reactants and products are indistinguishable. D) The number of product and reactant molecules are the same. Chem Review - 2

20. 18) What is the relationship between the amu and the gram? A) One gram is always greater than 1 amu. B) One amu is visible to the naked eye. C) One gram is equal to 1 amu. D) One amu is always greater than 1 gram. Chem Review - 2

21. 19) Which has the greatest number of atoms? A) 38 g of fluorine, F2 B) 16 g of methane, CH4 C) 34 g of ammonia, NH3 D) 32 g of oxygen, O2 Chem Review - 2

22. 20) A substance whose formula does not contain OH yet which yields a basic solution when dissolved is A) NH3 B) NaCl C) CO2 D) HCl Chem Review - 2

23. 21) What salt is formed when a solution of sodium hydroxide, NaOH, is neutralized by sulfuric acid, H2SO4? A) NaH B) NaSO4 C) H-OH D) Na2SO4 Chem Review - 2

24. 22) If a weak acid has a small tendency to lose hydrogen ions, then a weak base A) has a small tendency to give them back. B) has a small tendency to gain them. C) Both of the above are correct. D) Neither of the above is correct. Chem Review - 2

25. 23) Pure water contains A) only H3O+ ions. B) only HO- ions C) neither H3O+ nor HO- ions. D) both H3O+ and HO- ions Chem Review - 2

26. 24) When a hydronium ion concentration equals 1 mol/L, what is the pH of the solution? A) 0 B) not possible to calculate C) 1 D) 10 Chem Review - 2

27. 25) When a hydronium ion concentration equals 1 þ 10-5 mol/L, what is the pH of the solution? A) 12 B) 2 C) 9 D) 5 Chem Review - 2

28. 26) The two components that make up a buffer include A) a weak acid and the salt of this weak acid. B) a strong acid and a strong base. C) a strong acid and a weak acid. D) weak acids and a weak base. Chem Review - 2

29. 27) Which of the following statements is true? A) Reducing agents cannot be oxidized. B) Oxidizing agents are reduced when they oxidize. C) Reducing agents are reduced when they oxidize. D) Oxidizing agents cannot be oxidized. Chem Review - 2

30. Good Luck and Happy Holidays • Chamos • Christmas • Dongii • Dosmoche • Ganna • Hanukkah • Kwanzaa • Ramadan • Or whatever winter solstice holiday you celebrate. Chem Review - 2